Acrylic fiber has excellent properties in heat retention, form stability, light resistance, texture, dyeing, etc. and, due to its excellent physical properties and easy-care property, which are not available in the natural fibers, it has been widely utilized in clothing and interior use. However, the acrylic fiber as such still has some problems such as, due to its poor hygroscopicity, static electricity is apt to be generated by friction, dust is apt to stick to the clothing by electrostatic force and unpleasant feeling is noted due to the discharge of electrostatic force upon putting on and taking off the clothing. Various attempts have been already conducted up to now for solving the problems above. The most common attempt is a method where an oiling agent having antistatic property is applied on the fiber surface but, in this method, although an excellent antistatic property is available in the fiber's initial stage, the antistatic property lowers significantly by dyeing, repeated bleaching, washing, etc. of the fiber. As an example of an attempt for achieving a fiber having durable antistatic property, there is proposed in Patent Document 1 a method of spinning an acrylonitrile copolymer prepared by copolymerization of a vinyl monomer having a glyoxyl group. However, it is essential in such a method that the acrylonitrile copolymer is copolymerized with another specific monomer, whereby complexity in the polymerizing operation is unable to be avoided and, moreover, due to copolymerization of a monomer having a strong hydrophilic property, such copolymer is apt to be eluted during a spinning step, particularly during the steps of coagulating to water washing, and the contamination of the solvent to be recovered and reused is significant.
There is also proposed a method where fine particles having electrical conductivity, such as electroconductive carbon and other metal compounds are kneaded into fiber to prepare a so-called electroconductive fiber. For example, there is proposed a method in Patent Document 2 of a solution of acrylonitrile copolymer in an organic solvent, wherein carbon black is dispersed and contained, and a spinning dope of an acrylonitrile copolymer is mixed and spun. However, due to the use of carbon, the fiber prepared by such a method is black or gray in color, whereby the useful range of the fiber such as in clothing and interior use is significantly restricted. In Patent Document 3, there is proposed a method where an electroconductive acrylic fiber is prepared by a core-sheath complex spinning method using an electroconductive substance having an electric conductivity of not less than 10−3 S/cm but, since a core-sheath spinning apparatus having a complicated shape is necessary for this method, problems such as high cost for the equipment and significant lowering of productivity arises. In Patent Document 4, there is proposed a method where alkali metal salt and water are added to a mixture of acrylonitrile copolymer and acrylonitrile antistatic polymer, followed by dissolving the mixture in an organic solvent and the resulting spinning dope is spun. Although the half-life of the woven product comprising the fiber prepared by such a method is long, the product is insufficient as an antistatic fiber. Moreover, in accordance with such a method, there is a problem that the alkali metal ion is ionically bound to the dyeing site and is easily detached during a step of spinning and washing with water or during a step of dyeing.